During wireless data transmission, service data (for example, speech, a video, other data carried in the form of an IP packet), a signaling message that is between wireless devices, and the like usually need to be encoded and modulated first before they are transferred out in the manner of an electromagnetic wave. The encoding may comprise signal source encoding and channel encoding, and after channel encoding, processing such as interleaving may be further performed. A receiver obtains, by using processes such as corresponding de-interleaving (if any), decoding, and demodulation, data that is actually transmitted by a sender. In each transmission subframe, the sender device sends data to the receiver by using a data block (or may be referred to as a data unit, a data transmission block, and the like) as a unit.
During radio transmission, because of a factor such as interference that exists in a channel, an error may occur in data transmission. Retransmission is a mechanism in which a sender is enabled to resend data that encounters an error during transmission, to ensure that the receiver can correctly recover the data sent by the sender. In a data retransmission mechanism, usually, after sending a piece of data, the sender waits for a data reception indication of the receiver, and then decides whether the sender needs to retransmit data that the receiver does not receive correctly. For example, in an implementing manner, the receiver demodulates and decodes a received signal. If the signal is decoded correctly, the receiver sends correct reception indication information (Positive Acknowlegement) to the sender. If the signal is decoded incorrectly, the sender sends an incorrect reception signal (Negative Acknowlegement). In another implementing manner, only a correct reception indication information (Positive Acknowlegement) or only an incorrect receive signal (Negative Acknowlegement) may be sent, and the sender retransmits, according to these reception status indication information, data that the receiver does not receive correctly, so as to determine whether retransmission needs to be performed. However, in a common data retransmit mechanism, after it is determined that retransmission needs to be performed, a retransmitted unit is an entire data block (or referred to as a data unit, a data transmission block, and the like) obtained after channel encoding, and retransmission of the entire data block occupies a relatively large bandwidth resource.